The present invention relates to a mailer or business form having an imagable surface, and more particularly, to a mailer or business form including a coating of a first colorless reactant on one surface thereof and a transparent patch overlying the coating, the patch including a coating of a second colorless reactant on the surface facing the first coating such that when the transparent patch is impacted by an imaging force, a visible image is formed.
Mailers or business form assemblies typically comprise sealed envelopes which contain additional sheets therein on which information can be printed by impact printing processes. These mailers are frequently processed by computer-aided automated systems. The ability to print information selectively both on the inside and on the outside of the mailer simultaneously eliminates time-consuming separate printing of the sheets and envelopes, and manual stuffing, sealing, and stamping of individual envelopes. Mailers of this type are described in U.S. Pat. Nos. 3,777,971, 3,830,141, 3,988,971, 4,081,127, 4,095,965, 4,425,386, 4,705,298 and 4,729,506.
In producing this type of mailer or business form, confidential information, such as billing information, appears only on the inner layers of the mailer, while other information, such as the address, must appear on the outside. A number of techniques have been proposed to accomplish this result.
One prior method involves printing all of the information on the outside of the mailer and onto one or more interior sheets. The confidential information, which is to appear only on the inner layers, is then obscured by overprinting the confidential information on the exterior surface of the mailer with enough printed characters to make it unreadable. However, envelopes printed in this fashion have an undesirable appearance and require additional printing steps.
Another prior method involves the use of spot coatings of carbon ink on the bottom side of a top record sheet positioned over the mailer. Using this method, the address information can be printed on the front of the envelope by positioning it under the carbon spot, while confidential information can be printed onto the interior sheets. However, this system requires the use of expensive carbonizing bond paper to prevent penetration of the carbon ink. In addition, the top record sheet is typically thrown away because the information recorded there is usually stored on computer.
Another type of mailer uses a carbon ink spot coated carbon tissue which is placed between the top sheet and the mailer. This eliminates the use of expensive carbonizing bond paper, but the carbon tissue must be removed and thrown away prior to mailing.
Carbon ink spot coated carbonizing bond paper and carbon tissue sheets have sometimes been used inside the mailer. However, as discussed previously, these systems are expensive and, in addition, can cause smudging of the image receiving sheet.
Another system is disclosed in U.S. Pat. No. 4,172,605 which uses a chemically reactive ribbon for a typewriter or a computer printer. The ribbon is coated with a solution which reacts with the coating on portions of the mailer to form images. However, this system requires direct contact between the ribbon and the mailer so that the chemical reaction can take place. In addition, the ribbons, which are relatively expensive, must be replaced frequently.
Still another system is disclosed in Chang et al, U.S. Pat. No. 4,425,386. The mailer uses an autogenous, or self-contained, carbonless coating over part of the top sheet. The impact of the printer or typewriter causes the image to develop in the coated area. Other information printed at the same time but outside the coated area will not appear on the top sheet. The interior sheets of the mailer may have self-contained coatings or other printing systems so that the other information will appear on the appropriate sheets.
While the mailer described in the Chang patent solves some of the problems associated with mailers, it suffers some serious drawbacks. The Chang patent teaches the use of a typical self-contained coating, which contains an encapsulated color former dissolved in oil and a dispersed color developer, such as phenolic resin or acid clay. However, such self-contained coatings suffer from a number of disadvantages. One problem with typical self-contained coatings is that dispersions of color developer usually must be applied as low solids content dispersions due to the poor rheology (i.e., high viscosity) of commercially available phenolic dispersions. The low solids level results in higher drying requirements, weak image development, and sheet distortion upon drying. Poor rheology also limits the method of applying these coatings by air knives or other full coat applicators, effectively preventing their use as spot coatings. In some cases, the addition of high levels of binder to the coating may permit it to be printed as a spot coating, but this results in poor image development.
Background coloration is also a major problem with conventional self-contained coatings. The existence of free color former in the coating remaining after the encapsulation process causes premature coloration of the background when it reacts with the dispersed color developer which is also present. Additional background coloration can be caused by the tendency of phenolic resin dispersions to yellow when exposed to air. Premature coloration of the color former microcapsules may also result due to their rupture by pressures such as minor abrasions and friction applied to the paper during storage, transportation and routine handling.
Another problem with typical self-contained coatings is the waste of expensive color forming dyes. Much of the dissolved dye remains in the capsules and is not available for reaction with the color developer when the capsules are ruptured. This requires the use of higher coating weights to achieve a sufficient surface concentration of dye and results in a significant waste of dye.
Van Malderghem, U.S. Pat. No. 4,705,298 discloses a self-imaging web including a coating containing dye microcapsules and an acidic co-reactant positioned behind the window cut area of an envelope face web such that when the self-imaging web is impacted, address information may be viewed through the window area. However, additional steps are required to provide die cut windows on the envelope. In addition, a separate continuous web is required to form window patches over the die cut windows.
Neubauer, U.S. Pat. No. 4,729,506, teaches yet another variation of carbonless coatings in which a continuous mailer assembly is provided comprising a front ply having a cut-out window, a transparent patch secured over the window, an insert ply and a back ply. The patch is provided with a CB coating on its under surface while the upper surface of the uppermost insert ply is provided with a CF coating such that when pressure is applied to the patch, the CB coating reacts with the CF coating to form an image on the mailer which can be viewed through the patch. However, the mailer construction requires both a separate coated insert ply and front ply including a cut-out window and patch.
Accordingly, there is still a need in the art for a mailer or business form having an imagable area which allows information to be printed and viewed without the need for die cut windows, additional webs or plies, and without the drawbacks of self-contained coatings